System and method for a prosthetic hand having sensored brushless motors

Abstract

A system and method for a prosthetic assembly that includes a first prosthetic component, comprising a prosthetic hand base; a set of second prosthetic components, comprising a set of prosthetic fingers, and a set of actuating systems, wherein one actuating system connects a pair of distinct prosthetic components, enabling actuation of one prosthetic component with respect to the other. Each actuating system, from the set of actuating systems, includes a linkage and a sensored brushless motor; wherein the sensored brushless motor comprises a brushless motor, a field oriented control system, a rotary encoder, and a gearbox.

We claim: 
     
       1. A prosthetic assembly system comprising:
 a prosthetic hand, comprising: a hand base, and a set of prosthetic fingers; and 
 a set of actuating systems, wherein each actuating system connects a prosthetic finger to the hand base and provides locomotion for actuation of the prosthetic finger with respect to the hand base, and each actuating system comprises:
 a linkage that mechanically couples the prosthetic finger to the hand base, and 
 a sensored brushless motor, comprising a brushless motor, a field oriented control (FOC) control system, a rotary encoder, and a gearbox. 
 
 
     
     
       2. The system of  claim 1 , wherein the rotary encoder is tunneling magnetoresistance (TMR) sensor. 
     
     
       3. The system of  claim 2 , wherein the brushless motor further comprises a disk magnet situated on the back shaft of the brushless motor, and the TMR sensor is axially calibrated to the brushless motor along the back shaft and positioned such that the TMR sensor is proximal to the disk magnet with a defined gap between the TMR sensor and the disk magnet. 
     
     
       4. The system of  claim 1 , wherein the set of prosthetic fingers comprises five prosthetic fingers. 
     
     
       5. The system of  claim 4 , wherein one prosthetic finger from the set of prosthetic fingers is a thumb prosthetic finger, comprising two thumb components; wherein one actuating system couples to each thumb component. 
     
     
       6. The system of  claim 1 , wherein the sensored brushless motor for each prosthetic finger is identically calibrated, such that each brushless motor is calibrated to its respective rotary encoder to the same initial position, such that the calibration for all prosthetic fingers is synchronized. 
     
     
       7. The system of  claim 6 , wherein any prosthetic finger from the set of prosthetic fingers is hot-swappable, such that it may be removed and replaced with a new prosthetic finger without any additional calibrations. 
     
     
       8. The system of  claim 1 , wherein all FOC control systems from the set of actuating systems are implemented on a single printed circuit board positioned in the prosthetic hand base. 
     
     
       9. The system of  claim 1 , wherein the gearbox comprises a worm drive gearbox. 
     
     
       10. The system of  claim 1 , wherein the linkage comprises a compliant 4-bar linkage. 
     
     
       11. The system of  claim 1 , wherein the system further comprises a control input, controllably coupled to sensored brushless motors configured to perform simultaneous and independent actuation of the sensored brushless motors. 
     
     
       12. The system of  claim 1 , wherein the system further comprises a set of sensored brushless motor housings, wherein for each sensored brushless motor, the brushless motor and the rotary encoder are encased in the sensored brushless motor housings; and wherein each sensored brushless motor housing is positioned within the prosthetic hand base. 
     
     
       13. The system of  claim 12 , wherein each sensored brushless motor housing is removable from the prosthetic hand base. 
     
     
       14. A method for implementing brushless motors with a prosthetic assembly for a prosthetic hand comprising:
 integrating an encoder with a brushless motor, comprising:
 fixing a diametrically magnetized magnet to the motor rotor, and 
 mounting an encoder above the magnet, such that the encoder is axially aligned with the motor; 
 calibrating the brushless motor with the encoder; 
 embedding the motor between a first prosthetic component and a second prosthetic component, wherein the first prosthetic component comprises a hand base and the second prosthetic component comprises a prosthetic finger; and 
 controlling the motor through a field oriented control (FOC) mode. 
 
 
     
     
       15. The method of  claim 14 , wherein calibrating the sensored brushless motor comprises:
 measuring a rotational actuation of the rotor in two opposing directions, thereby determining a rotor offset, wherein the offset comprises the difference in the measured rotational actuations of the two opposing directions, and 
 minimizing the rotor offset, comprising reducing the rotor offset such that it is below a desired threshold. 
 
     
     
       16. The method of  claim 15 , wherein measuring a rotational actuation of the rotor in two opposing directions comprises:
 actuating the motor in one direction with a fixed amount of power and measuring the average rotor speed of the motor during the entire actuation, and 
 actuating the motor in the opposite direction with the fixed amount of power and measuring the average rotor speed of the motor during the entire actuation. 
 
     
     
       17. The method of  claim 15 , wherein measuring a rotational actuation of the rotor in two opposing directions comprises
 actuating the motor in one direction with a fixed amount of power and measuring the angular displacement of the motor during the entire actuation, and 
 actuating the motor in the opposite direction with the fixed amount of power and measuring the angular displacement of the motor during the entire actuation. 
 
     
     
       18. The method of  claim 15 , wherein the sensored brushless motor is encased in a housing, and minimizing the rotor offset comprises rotating the encoder such that the rotor offset is reduced. 
     
     
       19. The method of  claim 14 , wherein the sensored brushless motor is encased in a housing and the embedding the motor between a first prosthetic component and a second prosthetic component, comprises, for each finger of the prosthetic hand, positioning the housing within the hand base in proximity of the prosthetic finger.